Adds support to control the PWM bus available in official Raspberry Pi
PoE HAT. Only RPi's co-processor has access to it, so commands have to
be sent through RPi's firmware mailbox interface.
Signed-off-by: Nicolas Saenz Julienne <[email protected]>
---
Changes since v1:
- Use default pwm bindings and get rid of xlate() function
- Correct spelling errors
- Correct apply() function
- Round values
- Fix divisions in arm32 mode
- Small cleanups
- Add comment explaining weird Kconfig construct
drivers/pwm/Kconfig | 9 ++
drivers/pwm/Makefile | 1 +
drivers/pwm/pwm-raspberrypi.c | 221 ++++++++++++++++++++++++++++++++++
3 files changed, 231 insertions(+)
create mode 100644 drivers/pwm/pwm-raspberrypi.c
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 63be5362fd3a..b0ffb1e690c0 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -379,6 +379,15 @@ config PWM_PXA
To compile this driver as a module, choose M here: the module
will be called pwm-pxa.
+config PWM_RASPBERRYPI
+ tristate "Raspberry Pi Firwmware PWM support"
+ # Make sure not 'y' when RASPBERRYPI_FIRMWARE is 'm'. This can only
+ # happen when COMPILE_TEST=y, hence the added !RASPBERRYPI_FIRMWARE.
+ depends on RASPBERRYPI_FIRMWARE || (COMPILE_TEST && !RASPBERRYPI_FIRMWARE)
+ help
+ Enable Raspberry Pi firmware controller PWM bus used to control the
+ official RPI PoE hat
+
config PWM_RCAR
tristate "Renesas R-Car PWM support"
depends on ARCH_RENESAS || COMPILE_TEST
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index cbdcd55d69ee..b557b549d9f3 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -35,6 +35,7 @@ obj-$(CONFIG_PWM_MXS) += pwm-mxs.o
obj-$(CONFIG_PWM_OMAP_DMTIMER) += pwm-omap-dmtimer.o
obj-$(CONFIG_PWM_PCA9685) += pwm-pca9685.o
obj-$(CONFIG_PWM_PXA) += pwm-pxa.o
+obj-$(CONFIG_PWM_RASPBERRYPI) += pwm-raspberrypi.o
obj-$(CONFIG_PWM_RCAR) += pwm-rcar.o
obj-$(CONFIG_PWM_RENESAS_TPU) += pwm-renesas-tpu.o
obj-$(CONFIG_PWM_ROCKCHIP) += pwm-rockchip.o
diff --git a/drivers/pwm/pwm-raspberrypi.c b/drivers/pwm/pwm-raspberrypi.c
new file mode 100644
index 000000000000..72dc0fc5a206
--- /dev/null
+++ b/drivers/pwm/pwm-raspberrypi.c
@@ -0,0 +1,221 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2020 Nicolas Saenz Julienne <[email protected]>
+ * For more information on Raspberry Pi's PoE hat see:
+ * https://www.raspberrypi.org/products/poe-hat/
+ *
+ * Limitations:
+ * - No disable bit, so a disabled PWM is simulated by duty_cycle 0
+ * - Only normal polarity
+ * - Fixed 12.5 kHz period
+ *
+ * The current period is completed when HW is reconfigured.
+ */
+
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+
+#include <soc/bcm2835/raspberrypi-firmware.h>
+#include <dt-bindings/pwm/raspberrypi,firmware-pwm.h>
+
+#define RPI_PWM_MAX_DUTY 255
+#define RPI_PWM_PERIOD_NS 80000 /* 12.5 kHz */
+
+#define RPI_PWM_CUR_DUTY_REG 0x0
+#define RPI_PWM_DEF_DUTY_REG 0x1
+
+struct raspberrypi_pwm {
+ struct rpi_firmware *firmware;
+ struct pwm_chip chip;
+ unsigned int duty_cycle;
+};
+
+struct raspberrypi_pwm_prop {
+ __le32 reg;
+ __le32 val;
+ __le32 ret;
+} __packed;
+
+static inline struct raspberrypi_pwm *to_raspberrypi_pwm(struct pwm_chip *chip)
+{
+ return container_of(chip, struct raspberrypi_pwm, chip);
+}
+
+static int raspberrypi_pwm_set_property(struct rpi_firmware *firmware,
+ u32 reg, u32 val)
+{
+ struct raspberrypi_pwm_prop msg = {
+ .reg = cpu_to_le32(reg),
+ .val = cpu_to_le32(val),
+ };
+ int ret;
+
+ ret = rpi_firmware_property(firmware, RPI_FIRMWARE_SET_POE_HAT_VAL,
+ &msg, sizeof(msg));
+ if (ret)
+ return ret;
+ else if (msg.ret)
+ return -EIO;
+
+ return 0;
+}
+
+static int raspberrypi_pwm_get_property(struct rpi_firmware *firmware,
+ u32 reg, u32 *val)
+{
+ struct raspberrypi_pwm_prop msg = {
+ .reg = reg
+ };
+ int ret;
+
+ ret = rpi_firmware_property(firmware, RPI_FIRMWARE_GET_POE_HAT_VAL,
+ &msg, sizeof(msg));
+ if (ret)
+ return ret;
+ else if (msg.ret)
+ return -EIO;
+
+ *val = le32_to_cpu(msg.val);
+
+ return 0;
+}
+
+static void raspberrypi_pwm_get_state(struct pwm_chip *chip,
+ struct pwm_device *pwm,
+ struct pwm_state *state)
+{
+ struct raspberrypi_pwm *rpipwm = to_raspberrypi_pwm(chip);
+
+ state->period = RPI_PWM_PERIOD_NS;
+ state->duty_cycle = DIV_ROUND_CLOSEST(rpipwm->duty_cycle * RPI_PWM_PERIOD_NS,
+ RPI_PWM_MAX_DUTY);
+ state->enabled = !!(rpipwm->duty_cycle);
+ state->polarity = PWM_POLARITY_NORMAL;
+}
+
+static int raspberrypi_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+ const struct pwm_state *state)
+{
+ struct raspberrypi_pwm *rpipwm = to_raspberrypi_pwm(chip);
+ unsigned int duty_cycle;
+ int ret;
+
+ if (state->period < RPI_PWM_PERIOD_NS ||
+ state->polarity != PWM_POLARITY_NORMAL)
+ return -EINVAL;
+
+ if (!state->enabled)
+ duty_cycle = 0;
+ else if (state->duty_cycle < RPI_PWM_PERIOD_NS)
+ duty_cycle = DIV_ROUND_CLOSEST_ULL(state->duty_cycle * RPI_PWM_MAX_DUTY,
+ RPI_PWM_PERIOD_NS);
+ else
+ duty_cycle = RPI_PWM_MAX_DUTY;
+
+ if (duty_cycle == rpipwm->duty_cycle)
+ return 0;
+
+ ret = raspberrypi_pwm_set_property(rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,
+ duty_cycle);
+ if (ret) {
+ dev_err(chip->dev, "Failed to set duty cycle: %d\n", ret);
+ return ret;
+ }
+
+ /*
+ * This sets the default duty cycle after resetting the board, we
+ * updated it every time to mimic Raspberry Pi's downstream's driver
+ * behaviour.
+ */
+ ret = raspberrypi_pwm_set_property(rpipwm->firmware, RPI_PWM_DEF_DUTY_REG,
+ duty_cycle);
+ if (ret) {
+ dev_err(chip->dev, "Failed to set default duty cycle: %d\n", ret);
+ return ret;
+ }
+
+ rpipwm->duty_cycle = duty_cycle;
+
+ return 0;
+}
+
+static const struct pwm_ops raspberrypi_pwm_ops = {
+ .get_state = raspberrypi_pwm_get_state,
+ .apply = raspberrypi_pwm_apply,
+ .owner = THIS_MODULE,
+};
+
+static int raspberrypi_pwm_probe(struct platform_device *pdev)
+{
+ struct device_node *firmware_node;
+ struct device *dev = &pdev->dev;
+ struct rpi_firmware *firmware;
+ struct raspberrypi_pwm *rpipwm;
+ int ret;
+
+ firmware_node = of_get_parent(dev->of_node);
+ if (!firmware_node) {
+ dev_err(dev, "Missing firmware node\n");
+ return -ENOENT;
+ }
+
+ firmware = rpi_firmware_get(firmware_node);
+ of_node_put(firmware_node);
+ if (!firmware)
+ return -EPROBE_DEFER;
+
+ rpipwm = devm_kzalloc(&pdev->dev, sizeof(*rpipwm), GFP_KERNEL);
+ if (!rpipwm)
+ return -ENOMEM;
+
+ rpipwm->firmware = firmware;
+ rpipwm->chip.dev = dev;
+ rpipwm->chip.ops = &raspberrypi_pwm_ops;
+ rpipwm->chip.base = -1;
+ rpipwm->chip.npwm = RASPBERRYPI_FIRMWARE_PWM_NUM;
+
+ platform_set_drvdata(pdev, rpipwm);
+
+ ret = raspberrypi_pwm_get_property(rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,
+ &rpipwm->duty_cycle);
+ if (ret) {
+ dev_err(dev, "Failed to get duty cycle: %d\n", ret);
+ return ret;
+ }
+
+ return pwmchip_add(&rpipwm->chip);
+}
+
+static int raspberrypi_pwm_remove(struct platform_device *pdev)
+{
+ struct raspberrypi_pwm *rpipwm = platform_get_drvdata(pdev);
+ int ret;
+
+ ret = pwmchip_remove(&rpipwm->chip);
+ if (!ret)
+ rpi_firmware_put(rpipwm->firmware);
+
+ return ret;
+}
+
+static const struct of_device_id raspberrypi_pwm_of_match[] = {
+ { .compatible = "raspberrypi,firmware-pwm", },
+ { }
+};
+MODULE_DEVICE_TABLE(of, raspberrypi_pwm_of_match);
+
+static struct platform_driver raspberrypi_pwm_driver = {
+ .driver = {
+ .name = "raspberrypi-pwm",
+ .of_match_table = raspberrypi_pwm_of_match,
+ },
+ .probe = raspberrypi_pwm_probe,
+ .remove = raspberrypi_pwm_remove,
+};
+module_platform_driver(raspberrypi_pwm_driver);
+
+MODULE_AUTHOR("Nicolas Saenz Julienne <[email protected]>");
+MODULE_DESCRIPTION("Raspberry Pi Firwmare Based PWM Bus Driver");
+MODULE_LICENSE("GPL v2");
--
2.28.0
On Thu, Oct 22, 2020 at 9:05 PM Nicolas Saenz Julienne
<[email protected]> wrote:
>
> Adds support to control the PWM bus available in official Raspberry Pi
> PoE HAT. Only RPi's co-processor has access to it, so commands have to
> be sent through RPi's firmware mailbox interface.
> drivers/pwm/pwm-raspberrypi.c | 221 ++++++++++++++++++++++++++++++++++
Name is completely confusing.
Please, make it unique enough to understand that this is exactly the
device it serves for.
For example, pwm-rpi-poe is better.
...
> + * - Only normal polarity
Can't it be emulated? Isn't it 100% - duty cycle % ?
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
...
> + ret = rpi_firmware_property(firmware, RPI_FIRMWARE_SET_POE_HAT_VAL,
> + &msg, sizeof(msg));
> + if (ret)
> + return ret;
> + else if (msg.ret)
Redundant 'else'
> + return -EIO;
...
> + ret = rpi_firmware_property(firmware, RPI_FIRMWARE_GET_POE_HAT_VAL,
> + &msg, sizeof(msg));
> + if (ret)
> + return ret;
> + else if (msg.ret)
Ditto.
> + return -EIO;
...
> + firmware_node = of_get_parent(dev->of_node);
> + if (!firmware_node) {
> + dev_err(dev, "Missing firmware node\n");
> + return -ENOENT;
> + }
> +
> + firmware = rpi_firmware_get(firmware_node);
> + of_node_put(firmware_node);
> + if (!firmware)
> + return -EPROBE_DEFER;
Looks like a hack.
...
> + ret = pwmchip_remove(&rpipwm->chip);
> + if (!ret)
> + rpi_firmware_put(rpipwm->firmware);
> +
> + return ret;
Can't you use the usual pattern?
ret = ...
if (ret)
return ret;
...
return 0;
--
With Best Regards,
Andy Shevchenko
Hi Andy, thanks for the review!
On Thu, 2020-10-22 at 21:53 +0300, Andy Shevchenko wrote:
> On Thu, Oct 22, 2020 at 9:05 PM Nicolas Saenz Julienne
> <[email protected]> wrote:
> > Adds support to control the PWM bus available in official Raspberry Pi
> > PoE HAT. Only RPi's co-processor has access to it, so commands have to
> > be sent through RPi's firmware mailbox interface.
> > drivers/pwm/pwm-raspberrypi.c | 221 ++++++++++++++++++++++++++++++++++
>
> Name is completely confusing.
> Please, make it unique enough to understand that this is exactly the
> device it serves for.
>
> For example, pwm-rpi-poe is better.
Sounds reasonable, I'll change that.
>
> ...
>
> > + * - Only normal polarity
>
> Can't it be emulated? Isn't it 100% - duty cycle % ?
I guess it can, OTOH given the rather specific use case, I doubt it'll be
worth the effort.
> > +#include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/pwm.h>
>
> ...
>
> > + ret = rpi_firmware_property(firmware, RPI_FIRMWARE_SET_POE_HAT_VAL,
> > + &msg, sizeof(msg));
> > + if (ret)
> > + return ret;
> > + else if (msg.ret)
>
> Redundant 'else'
Noted.
> > + firmware_node = of_get_parent(dev->of_node);
> > + if (!firmware_node) {
> > + dev_err(dev, "Missing firmware node\n");
> > + return -ENOENT;
> > + }
> > +
> > + firmware = rpi_firmware_get(firmware_node);
> > + of_node_put(firmware_node);
> > + if (!firmware)
> > + return -EPROBE_DEFER;
>
> Looks like a hack.
This is the pattern we've been using on all firmware dependent devices so far.
Feel free to suggest a better way, I'll be happy to look into it.
>
> ...
>
> > + ret = pwmchip_remove(&rpipwm->chip);
> > + if (!ret)
> > + rpi_firmware_put(rpipwm->firmware);
> > +
> > + return ret;
>
> Can't you use the usual pattern?
Yes of course. Don't know why I went this way.
Regards,
Nicolas